1. Field of the Invention
The present invention relates to a structure for mounting a telescopic antenna for an automobile, such as a passenger car.
2. Description of Related Art
The antennas for automobiles are generally structured by telescopic-jointed rods, free to extend and contract. This kind of antenna is mounted as follows. As shown in FIG. 5, a spacer pipe 24 is monolithically fitted in a conducting pipe 23, an outermost rod 2c is slidably fitted in and supported by the spacer pipe 24, a base pipe 27 is monolithically fitted over the conducting pipe 23, and a nut 28 is fastened onto a threaded portion 27a of the base pipe 27. In this structure, the conducting pipe 23 and the spacer pipe 24 have to be connected rigidly but nonconductingly by fastening the nut 28. Therefore, in a conventional structure, a flange 23a and a collar 24a provided on the pipes 23, 24 are clamped by the top rim of the base pipe 27 and a contact portion 28a of the nut 28. The flange 23a of the conducting pipe 23 has a round surface since it is shaped by expanding the rim portion. In short, the spacer pipe's collar 24a bears directly against the round flange 23a. Consequently, when the spacer pipe's collar 24a is deformed by fastening the nut 28 too tightly, the plastic deformation is directed inwards along the round surface of the flange 23a, narrowing the spacer pipe 24. In this case, the friction between the outermost rod 2c and the spacer pipe 24 becomes greater and the sliding of the outmost rod 2c will be hindered.
The spacer pipe 24 has to be fitted in the conducting pipe 23 and attached in position so as not to come off. In a usual method for attaching, the conducting pipe 23 with the spacer pipe 24 fitted in is processed by embossing or curl staking so that the processed part engages with the recessed portion 24b of the spacer pipe 24. Not only is the process complicated and labor-consuming, but the pipes may deform, with the circularity decreasing, or even break under the process load. Again, the easy sliding of the outermost rod will thus be hindered. Or, in this method, insufficient or not-deep-enough insertion of the spacer pipe into the conducting pipe may occur, and then the insufficiently assembled pipes may go into the process for attaching the spacer pipe 24 in position.